1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine or a laser printer, and in particular relates to an apparatus having a door member and a transfer unit.
2. Description of the Related Art
There has been provided a multi-color image forming apparatus called a tandem type (or an inline type) which typically has a plurality of photosensitive drums placed in a line. This tandem type image forming apparatus mainly includes a transverse configuration in that the photosensitive drums are arranged in a horizontal direction and a longitudinal configuration in that the drums are arranged in a vertical direction. The longitudinal configuration can be reduced in occupied area although the height is increased in comparison with the transverse configuration, so that it has an advantage in usability for jam disposal, for example.
FIG. 8 shows a conventional longitudinal full-color image forming apparatus. Reference numerals 101a, 101b, 101c, and 101d denote process cartridges for each color; numeral 102 denotes a transfer unit for transferring image by carrying and conveying a sheet S with a belt 102a; and numeral 103 a fuser. Images formed by the process cartridges 101a, 101b, 101c, and 101d are transferred on the sheet S carried by the transfer unit 102, and the sheet S carrying the transferred image is discharged out of the apparatus after passing through the fuser 103. When a door 104 is opened, the process cartridges 101a, 101b, 101c, and 101d are exposed, facilitating component replacement and jam disposal.
However, in the conventional example mentioned above, when doing maintenance on the backside of the transfer unit 102 (adjacent to the door of the belt 102a), the accessibility to this region is difficult because the space between the transfer unit 102 and the door 104 is comparatively small. For example, as shown in FIG. 8, in an apparatus having a sheet conveying unit 105 for double-sided printing arranged on the backside of the transfer unit 102, the space for having access to the sheet conveying unit 105 is very limited. Hence, the disposal of a jam generated in the sheet conveying unit 105 has been very difficult.